Historically, external heating, ventilation, and air conditioning ("HVAC") and analogous equipment have been mounted on concrete blocks or pads. These pads isolate the equipment from contaminants such as dirt, debris, and moisture typically present on the adjacent ground, thereby reducing the detrimental effects of such contaminants on the operation of the equipment. The pads additionally may dampen at least some ground- or equipment-based vibrations, diminishing the likelihood of damage caused by the vibrations to the mounted equipment, and decrease or prevent settling of the equipment into the soil itself.
Although useful for these purposes, concrete pads are both expensive to create (if formed on-site) and difficult to transport (if pre-cast). Pouring concrete is, of course, labor intensive, requiring substantial human effort to form a suitable pad. While pre-cast concrete bases may be less expensive to construct, their weight and brittleness likely increase transportation-related difficulties and cost.
To avoid these problems associated with conventional concrete pads, U.S. Pat. No. 4,505,449 to Turner, et al. ("the Turner patent") describes a composite equipment base having a core of expanded polystyrene ("EPS"). According to the Turner patent, use of EPS decreases the weight of the base by as much as seven-eighths of the weight of a (solid) concrete base of equivalent size. Applied to the sides and top of the EPS core is a "concrete coating" of "a fiberglass/cement composition using alkali resistant fiberglass strands." See col. 2, lines 32-34. Although denominated a "low density" composite material, the resulting structure nonetheless "appears to be an ordinary solid concrete slab" when viewed in use. See col. 1, lines 43-44.
The Turner patent additionally mentions possibly applying "a thin coating of cementitious material . . . to the core bottom." See col. 2, lines 50-52. The existence of such coating appears not to be preferable, however, as it counteracts advantageous characteristics of the base described in the Turner patent. For example, exposing the bottom of the EPS core purportedly permits it to act "as a cushion preventing damage to the top surface of the base stacked beneath the exposed bottom" during shipping. See id., lines 61-63. The exposed core
also allows for easier installation of the base since the polystyrene will conform to a ground configuration thus requiring less smoothing than that necessary for the installation of ordinary concrete bases.
See id., lines 64-68.
U.S. Pat. No. 5,333,830 to Millen ("the Millen patent") discloses another faux-concrete composite pad. As described in the Millen patent, the pad includes a cellular core embedded in a cementitious shell. A "bottom facing sheet" of undisclosed composition seals the core within the shell, its presence being masked by additional shell material so that, "from all outward appearances," the pad is "a solid block" of the cementitious material. See col. 4, lines 53-54. Discussed solely in the Abstract of the Millen patent is a feature of the cellular core, which purportedly "enables the pad to conform to a degree to surfaces on which the pad is placed." See Abstract, lines 13-14. The Millen patent fails to describe how such conformation can occur, however, particularly when both the facing sheet and rigid cementitious shell material encapsulate the core bottom.
Because directed to faux-concrete bases of decreased weight, the Turner and Millen patents otherwise disclose generally conventional equipment pad structures. FIGS. 1-3 of the Turner patent, for example, illustrate smooth-bottomed pads regardless of whether the EPS is exposed or, alternatively, coated with cementitious material. FIGS. 1-2 of the Millen patent likewise illustrate predominantly flat-bottomed structures with essentially no surface irregularities. The pads of these patents thus apparently rely solely on the weight of the mounted equipment (and possible compression of any exposed core) to seat them on the ground.